How we work it out
Length × width × depth gives cubic metres, and that's the whole sum. The judgment call is depth. 5 cm freshens up an existing bed, 7.5 cm is the standard for holding moisture, and 10 cm is what smothers weeds. Skimp on depth and you'll be back doing it again by Christmas.
Worked example: a 6 m × 2 m bed at 7.5 cm needs 0.9 m³. That's 18 bags at 50 L each, roughly $130 to $160 at the hardware shop, or one small bulk delivery at $50 to $100. Past about half a cube, bulk from a landscape yard nearly always wins.
Choosing your mulch
Chunky bark lasts longest and looks sharp. Pine bark is the budget all-rounder. Sugar cane and pea straw feed veggie beds as they break down, so replace them yearly and call it composting. Before you pay retail, ring the council, because many give away mulched green waste, and a local arborist will often drop a whole truckload of chip for nothing.
Common questions
How many 50 L bags of mulch in a cubic metre?
Twenty. If the maths says more than 10 or 12 bags, price up bulk delivery. It's usually half the cost per cubic metre and saves the boot of your car.
How deep should mulch be?
7.5 cm for general garden beds, or 10 cm if weed suppression is the goal. Keep it clear of plant stems and tree trunks, since mulch piled against bark invites rot.
How much does bulk mulch cost in Australia?
Commonly $55 to $110 per cubic metre delivered, depending on the type and how far you are from the yard. Premium barks run higher. Council and arborist chip can be free.
Sources
Electricity rates: AER Default Market Offer (NSW, SA, south-east QLD), Victorian Default Offer, and each remaining state's regulated tariff, current for 2026–27. Appliance figures: the energyrating.gov.au registration database (July 2026 snapshot). Methods and assumptions are described on each page.